Once you click the button the following dialog appears:
Use this dialog to browse for an image file or capture a new screenshot and define the image properties. To change the image properties, right-click the necessary image and select the Image properties menu option from the pop-up menu or double-click the required image to display this dialog.
Image source
Use this field to specify the type of the image: annotated screenshot, control image, control bullet, or a custom image. When you add a new image from a file, then Custom will be selected by default.
button the following dialog appears:
Press this button to add an image.
Press the button to close the dialog and to discard the changes.